Image display device and method for manufacturing the same

Abstract

Only a region where TFTs constituting a high-performance circuit will be disposed in a precursor semiconductor film PCS on an insulating substrate GLS with an insulating layer UCL serving as an undercoat is irradiated with a first energy beam LSR so as to be poly-crystallized while growing crystal grains laterally. Further a second rapid thermal treatment is performed all over the panel so as to reduce defects in the crystal grains in a region PSI poly-crystallized by the aforementioned energy beam. Thus, a high-quality polycrystalline semiconductor thin film serving as TFTs for a high-performance circuit and having a high on-current, a low threshold value, a low variation and a sharp leading edge characteristic is obtained. Concurrently, the precursor semiconductor layer in the other region is poly-crystallized by the second rapid thermal treatment so as to obtain a low-quality polycrystalline semiconductor thin film serving as pixel circuit TFTs and having a low on-current and properties of a low leak current and a high withstand voltage due to its high resistance. Accordingly, it is possible to form polycrystalline semiconductor TFTs high in driving performance and TFTs having properties of a low leak current and a high withstand voltage concurrently on one and the same insulating substrate.

1. A method for manufacturing an image display device including a pixel circuit serving as an image display portion, a drive circuit for driving the pixel circuit, an integrated circuit group for processing and converting an external input signal into a signal required for displaying an image, and transmitting the signal to the drive circuit, and an insulating substrate on which the pixel circuit, the drive circuit and the integrated circuit group are formed, the method comprising the steps of:
 scanning crystal grains with a first energy beam so as to grown the crystal grains in a direction of the scan to thereby form a polycrystalline semiconductor thin film of first crystal grains; and 
 performing a second rapid thermal treatment upon the polycrystalline semiconductor thin film of the first crystal grains so as to reduce defects in the crystal grains. 
 
     
     
       2. A method for manufacturing an image display device according to  claim 1 , wherein the second rapid thermal treatment is performed in a melting recrystallization method in which the semiconductor thin film is irradiated with a pulsed energy beam once or a plurality of times or in a solid-phase growth method using a rapid thermal annealing method. 
     
     
       3. A method for manufacturing an image display device according to  claim 1 , wherein a region other than the polycrystalline semiconductor thin film poly-crystallized while growing the first crystal grains in the direction of the scan and subjected to the second rapid thermal treatment to thereby reduce the defects in the crystal grains is polycrystalline with a crystal grain size ranging from about 10 nm to about 100 nm. 
     
     
       4. A method for manufacturing an image display device according to  claim 1 , wherein:
 the polycrystalline semiconductor thin film grown into the first crystal grains is formed in a method in which the semiconductor thin film is irradiated with an energy beam continuously or temporarily irradiated with an energy beam outputting energy for a fixed period once or a plurality of times so as to poly-crystallize the crystal grains while extending the crystal grains in the growing direction of the crystal grains; and 
 the second rapid thermal treatment is performed in a method in which the semiconductor thin film is irradiated with an energy beam having lower energy than the energy beam for a short time by one and the same apparatus for generating the energy beam. 
 
     
     
       5. A method for manufacturing an image display device according to  claim 1 , wherein a time when the semiconductor thin film is in a solid phase exists between the step of growing the first crystal grains in the direction of the scan with the first energy beam to thereby form a polycrystalline semiconductor thin film and the step of performing the second rapid thermal treatment so as to reduce defects in the crystal grains. 
     
     
       6. A method for manufacturing an image display device according to  claim 1 , wherein a time when the semiconductor thin film is in a liquid phase exists between the step of growing the first crystal grains in the direction of the scan with the first energy beam to thereby form a polycrystalline semiconductor thin film and the step of performing the second rapid thermal treatment so as to reduce defects in the crystal grains. 
     
     
       7. A method for manufacturing an image display device according to  claim 1 , wherein the polycrystalline semiconductor thin film grown into the first crystal grains is formed in a method in which the semiconductor thin film is irradiated with an energy beam outputting energy continuously or temporarily irradiated for a fixed period once or a plurality of times so as to poly-crystallize the crystal grains while extending the crystal grains in the growing direction. 
     
     
       8. A method for manufacturing an image display device according to  claim 1 , wherein the polycrystalline semiconductor thin film grown into the first crystal grains is formed in a method in which a catalyst such as metal is introduced into the semiconductor thin film or onto a surface or an interface thereof, and thermal energy is given thereto so as to accelerate poly-crystallization in the growing direction to thereby make the semiconductor thin film polycrystalline.